Synthesis and crystal structures of Cs5Nb2S4X9 - Double salts containing new cluster anions [Nb-2(mu-S-2)(2)X-8](4-) (X = Cl, Br)

Bis(disulfide)bridged Nb(+4) cluster halide complexes [Nb2S4X8](4-) (X = Cl , Br) were prepared by acid hydrolysis of [Nb2S4(NCS)(8)](4-) in concentrat ed aqueous HCl or HBr, solution from which they can be isolated as double s alts Cs-5[Nb2S4X8]X (X = Cl, 1; X = Br, 2). The crystal structures of 1 and 2 were determined. The isolation and Xray structure of oxonium salt (H3O)( 5) [Nb2S4Cl8]Cl (3) is also reported. 1-3 contain new [Nb2S4X8](4-) anions which can also be viewed as excised building blocks of polymeric solids NbS 2X2. The extra halogen resides in the center of octahedron formed by six Cs + or H3O+ ions. All the three salts are isostructural and crystallize in te tragonal space group Immm with the following parameters: a = 10.269(2), b = 16.343(2), c = 7.220(1)Angstrom for 1, a = 10.934(1), b = 16.613(2), c = 7 .470(1) Angstrom for 2, a = 9.639(1), b = 16.031(1), c = 7.071(1) Angstrom for 3. The parameters of the Nb2S4 core are only slightly affected by the c hange from Cl to Br.